Nuclear Theory·nucl-th

Monday·March 30, 2026

8 papers—2 primary·6 cross-listed

03
[Submitted on 26 Mar 2026] (cross-list from hep-ph)
Kaon Boer-Mulders function using a contact interaction
Dan-Dan Cheng🇨🇳 · Minghui Ding🇨🇳 · Daniele Binosi🇮🇹 · Craig D. Roberts🇨🇳
Using a symmetry preserving treatment of a vector*vector contact interaction (SCI), results are delivered for the four kaon transverse momentum dependent parton distribution functions (TMDs), viz. helicity-independent (HI) and Boer-Mulders (BM) TMDs for the kaon's $u$ , $s$ valence degrees of freedom. In completing this analysis, we are able to deliver insights into, amongst other things, the role played by emergent hadron mass (EHM) phenomena in producing these TMDs; the EHM modulating effect of the Higgs-boson coupling that produces the strange quark current mass; the impact of gauge link models on whether predictions satisfy the positivity constraint that bounds the BM function relative to the HI TMD; and the size of the BM shift and effects thereupon of off-diagonal terms in the associated scale-evolution kernel.
Comments:
16 pages, 7 figures, 2 tables
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2603.25941 [pdf]
3 citations
04
[Submitted on 26 Mar 2026] (cross-list from hep-th)
Efficient computation of the N-th rank QED polarization tensor: Universal worldline structure of form factors
Xabier Feal🇺🇸 · Andrey Tarasov🇺🇸 · Raju Venugopalan🇺🇸
We derived in arXiv:2206.04188 arXiv:2211.15712 a compact expression for the $N$ -th rank QED polarization tensor $Π_{μ_{1} \dots μ_{N}} (k_{1}, \dots, k_{N})$ in a $(0 + 1)$ -dimensional worldline framework. This fully off-shell object, a function of $N$ external photon four-momenta, is a key ingredient in high-order computations of cusp anomalous dimensions and lepton anomalous magnetic moments. We demonstrate here that $Π_{μ_{1} \dots μ_{N}}$ can further be expressed simply in terms of a small number of independent ``head" form factors (each representing $(N - 1)! /2$ Feynman diagrams) which have a universal structure in terms of sums over fermion Green functions and (propertime derivative of) their boson worldline superpartners. This worldline representation bypasses explicit Wick contractions and avoids tensor reductions to scalar loop integrals à la Passarino and Veltman, order by order in perturbation theory. We give explicit expressions for the $4$ -th and $6$ -th rank head form factors and provide a computer script generalizing these results to arbitrary $N$ external photons. The multiplicity of heads, and their growth with $N$ , can be understood in terms of orbits of the permutation group. We employ the Burnside-Cauchy-Frobenius lemma to show that it scales as $e^{N - 1} / N$ terms as opposed to the $e^{N - 1} N! / N$ terms in conventional perturbation theory. We reexpress worldline parameter integrals that define the $4$ -th rank heads as Feynman parameter integrals to reproduce the seminal results by Karplus and Neuman for the on-shell light-by-light amplitude and extend these to the fully off-shell case in massless QED employing a tailored integration-by-parts procedure. In a follow-up paper, we will discuss the direct computation of worldline integrals, potentially providing a further $N!$ advantage relative to Feynman diagram computations at high orders in perturbation theory.
Comments:
70 pages, 2 figures. The ancillary file headgen.py contains the computer script accompanying this manuscript
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2603.25962 [pdf]
PRD(2026)·0 citations
05
[Submitted on 27 Mar 2026] (cross-list from hep-ph)
(3+1)D dilute Glasma initial conditions in simulations of heavy-ion collisions
Kayran Schmidt🇦🇹
In this thesis, an approximation for the full (3+1)D dynamics of the Glasma is presented, which breaks boost-invariance on the level of the nuclear fields and leads to rapidity dependence in the final results. For this treatment, the Yang-Mills equations are linearized in covariant gauge, where lower-order, nonlinear contributions are neglected and the dynamics are captured by the (3+1)D dilute Glasma. The analytic solutions of the (3+1)D dilute Glasma are derived in both position and momentum space formulations, providing a comprehensive understanding of the involved (3+1)D dynamics. In position space, the field strength tensor results from the integration of free-streaming gluons that are produced in $2 \to 1$ scattering processes where the initial nuclear fields overlap. In momentum space, the event-averaged gluon number distribution for the (3+1)D dilute Glasma is derived in Coulomb gauge. A generalized, three-dimensional McLerran-Venugopalan nuclear model is developed for nuclei with realistic envelopes and intrinsic longitudinal correlations. Numerical results are presented for the rapidity structure of the energy-momentum tensor, the gluon number distribution, and the transverse energy of the (3+1)D dilute Glasma. In position space, the extended longitudinal collision geometry and finite longitudinal correlation length break boost-invariance. In momentum space, the results each follow universal parametrizations and are fixed by the values of two scaling parameters. Furthermore, the numerical results exhibit limiting fragmentation where the rapidity profiles approach a limiting distribution at large rapidities. This feature is also derived locally in position space for the analytic expressions of the field strength tensor and, in momentum space, for the transverse energy of the (3+1)D dilute Glasma.
Comments:
PhD Thesis, 217 pages, 43 figures, 4 tables. Abstract shortened to comply with arXiv guidelines. Supplemental material, raw data, raw plots, and plot scripts available from https://doi.org/10.5281/zenodo.18242275
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2603.26331 [pdf]
0 citations
06
[Submitted on 27 Mar 2026] (cross-list from hep-ph)
Neural network enhanced Bayesian global analysis of relativistic heavy ion collisions
Jussi Auvinen🇵🇱 · Kari J. Eskola🇫🇮 · Henry Hirvonen🇺🇸 · Harri Niemi🇫🇮
We introduce a novel deep convolutional neural network (NN) -enhanced Bayesian global analysis of bulk observables in highest-energy heavy-ion collisions, using relativistic 2+1 D second-order viscous hydrodynamics with a dynamical freeze-out, and with perturbative QCD and saturation -based initial conditions from the event-by-event EKRT-model. Our analysis has 13+2 free parameters for the QCD-matter properties + initial state, which are constrained by the experimental data from $s_{N N} = 200$ GeV Au+Au collisions at RHIC and $2.76$ TeV Pb+Pb, $5.02$ TeV Pb+Pb, and $5.44$ TeV Xe+Xe collisions at the LHC. We replace the computationally demanding hydrodynamical simulations by NNs, which predict bulk observables directly from the initial energy density profiles, event-by-event, and account for the QCD-matter properties. With the NN output, we train the Gaussian process emulators for obtaining centrality-class averaged observables and their uncertainties. The NNs reduce the computing time significantly, enabling us to include also statistics-hungry flow observables like $v_{4}$ and the normalized symmetric cumulant $N S C (4, 2)$ in the analysis. In this paper, we demonstrate the feasibility of the NN based Bayesian global analysis. We find the data favoring a specific shear viscosity $η / s$ with a minimum-value plateau at temperatures $150 ≲ T ≲ 230$ MeV, with $0.12 ≲ (η / s)_{min} ≲ 0.18$ . The bulk viscous coefficient $ζ / s$ is non-zero at $200 ≲ T ≲ 300$ MeV. The Knudsen number at the freeze-out is $0.8 - 2.3$ , while the ratio of the mean free path to the system size at freeze-out is in the range $0.3 - 1.2$ , implying that the freeze-out indeed happens at the expected limit of the applicability of hydrodynamics.
Comments:
29 pages, 17 figures. Published in Phys. Rev. C. The code for neural network training is available at Zenodo, DOI: 10.5281/zenodo.20499598
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2603.26413 [pdf]
PRC(2026)·1 citation
07
[Submitted on 27 Mar 2026] (cross-list from nucl-ex)
Probing Sub-MeV Dark Matter with Neutron-Capture $γ$ Spectroscopy
B. Meirose🇸🇪 · D. Milstead🇸🇪
We present a general, discovery-grade framework for searching for weakly coupled new particles emitted in nuclear de-excitation following neutron capture. Rather than relying on isolated spectral features, the method exploits correlated ``satellite-line combs'': multiple weak $γ$ -ray lines appearing at a common energy offset $Δ$ below known capture transitions. By combining likelihood information across many parent lines and multiple target nuclei, the approach strongly suppresses nuclear-structure ambiguities and instrumental artifacts. We also discuss optimal target selection and practical experimental implementation with high-resolution HPGe detectors.
Comments:
7 pages, 2 figures
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2603.26472 [pdf]
0 citations
08
[Submitted on 27 Mar 2026] (cross-list from hep-ph)
Non-eikonal corrections to dijet production in DIS
Néstor Armesto🇪🇸 · Fabio Domínguez🇪🇸 · Adrián Romero🇪🇸
We compute non-eikonal corrections to dijet production in deep inelastic scattering off a nucleus. Such corrections are expected to be quantitatively important at the energies of the future Electron Ion Collider. We focus on those corrections stemming solely from the finite longitudinal size of the nucleus. For both longitudinally and transversely polarized photons, we provide general, all-order expressions in terms of two-dimensional path integrals. To proceed further, we use the harmonic oscillator approximation for the target averages of Wilson lines. We then expand the general expressions order by order beyond the shockwave limit which provides the eikonal results, up to next-to-next-to-eikonal accuracy. We observe that next-to-eikonal corrections to this observable vanish for the mentioned approximation for target averages, as previously found for single gluon production in proton-nucleus collisions. Finally, we calculate the back-to-back of correlation limit of our expressions.
Comments:
48 pages, JHEP style
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2603.26526 [pdf]
0 citations

Affiliations

first authorsco-authorsvia INSPIRE

Kaon Boer-Mulders function using a contact interaction

Efficient computation of the N-th rank QED polarization tensor: Universal worldline structure of form factors

(3+1)D dilute Glasma initial conditions in simulations of heavy-ion collisions

Neural network enhanced Bayesian global analysis of relativistic heavy ion collisions

Probing Sub-MeV Dark Matter with Neutron-Capture γ Spectroscopy

Non-eikonal corrections to dijet production in DIS

Affiliations

Probing Sub-MeV Dark Matter with Neutron-Capture $γ$ Spectroscopy